#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

int main()
{
    int ret;
    ret = alarm(3);//because of the default system action of SIGALARM is abort the process,so the program exited after excuting pause() function
    printf("pause() return %d\n", pause());
    printf("I have been waken up. %d\n",ret);
}
